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ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution.

Wu A, Jing L, Wang J, Qu Y, Xie Y, Jiang B, Tian C, Fu H - Sci Rep (2015)

Bottom Line: Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE.As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition.The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin 150080 (P. R. China).

ABSTRACT
The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy "controlling competitive reaction" strategy by selecting the thiourea as S(2-) source and Zn(Ac)₂·2H₂O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m(2)g(-1), microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

No MeSH data available.


(a) the wide scan XPS spectrum and (b) the O1s XPS spectrum of PCMS-1, (c) XAES and (d) corresponding EXAFS spectra of PCMS-1.
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f3: (a) the wide scan XPS spectrum and (b) the O1s XPS spectrum of PCMS-1, (c) XAES and (d) corresponding EXAFS spectra of PCMS-1.

Mentions: To further demonstrate the presence of ZnO (Zn-O) in the PCMS-1, consequentially, the formation of ZnO-dotted structure, the XPS, Raman, IR and XAES test are performed because their high sensitivity to analyze the Zn-O or O. As shown in Figure 3a, the peaks belonging to O, S and Zn can be clearly seen in the wide scan spectrum, implying the presence of ZnO and ZnS in PCMS-1. Especially, the O1s XPS spectra can be deconvoluted into the three peaks (Figure 3b), in which the peak at 530.4 eV can be ascribed to the oxygen (OL) of ZnO32, which is a indicative of the presence of ZnO. The high resolution XPS spectrum in Figure S3 indicates that Zn 2p1/2 and 2p3/2 are located at 1042.95 eV and 1019.9 eV, which are characteristics for Zn2+33. In IR spectrum (Figure S4), a typical vibration of Zn–O bond in ZnO34 can be seen at about 500 cm−1 with noticeable intensity, indicating the presence of ZnO in the PCMS-1. Raman is a powerful tool for analyzing the structure of oxides. From the Figure S5, two obvious peaks can be observed at 557 cm−1 and 1126 cm−1. The peak at 557 cm−1 can be assigned to the E1 (LO) vibration model of hexagonal wurtzite structure ZnO crystal. While the peak at 1126 cm−1 is due to multiple phonon scattering processes of Zn-O. The peaks located at 420 cm−1 is from the E2 (high) vibration model of Zn-O35. The normalized XAES of PCMS-1 and corresponding EXAFS (extended x-ray absorption fine structure) are provided to give the further insight. The corresponding Fit parameters are shown in Table 1. We can see that the N value of Zn-S (N = 3.5) in PCMS-1 is close to that of standard ZnS (S-ZnS) (N = 4), indicating the existence of ZnS as the major phase of PCMS-1. The slight low N value of Zn-S (3.5 vs 4) also implies the presence of slight ZnO in PCMS-1. In addition, the lower N value of Zn-S-Zn (4.5) for PCMS-1 than that for S-ZnS (12) implies the small size of ZnS grain in PCMS-1. Notably, the Zn-O can be observed in PCMS-1 with N value of 1, more lower than 3.9 in bulk ZnO36. Generally, the low N value implies the small size of the particles. Typically, for single atom Ag chain, the N is 2, more lower than 12 for bulk Ag37. A single atom Pt has no shown any Pt–Pt contribution38. Therefore, the low N value of Zn-O implies the partial replacement of surface S atom in ZnS by O, and the formation of the ZnO-dotted ZnS clusters.


ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution.

Wu A, Jing L, Wang J, Qu Y, Xie Y, Jiang B, Tian C, Fu H - Sci Rep (2015)

(a) the wide scan XPS spectrum and (b) the O1s XPS spectrum of PCMS-1, (c) XAES and (d) corresponding EXAFS spectra of PCMS-1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4352920&req=5

f3: (a) the wide scan XPS spectrum and (b) the O1s XPS spectrum of PCMS-1, (c) XAES and (d) corresponding EXAFS spectra of PCMS-1.
Mentions: To further demonstrate the presence of ZnO (Zn-O) in the PCMS-1, consequentially, the formation of ZnO-dotted structure, the XPS, Raman, IR and XAES test are performed because their high sensitivity to analyze the Zn-O or O. As shown in Figure 3a, the peaks belonging to O, S and Zn can be clearly seen in the wide scan spectrum, implying the presence of ZnO and ZnS in PCMS-1. Especially, the O1s XPS spectra can be deconvoluted into the three peaks (Figure 3b), in which the peak at 530.4 eV can be ascribed to the oxygen (OL) of ZnO32, which is a indicative of the presence of ZnO. The high resolution XPS spectrum in Figure S3 indicates that Zn 2p1/2 and 2p3/2 are located at 1042.95 eV and 1019.9 eV, which are characteristics for Zn2+33. In IR spectrum (Figure S4), a typical vibration of Zn–O bond in ZnO34 can be seen at about 500 cm−1 with noticeable intensity, indicating the presence of ZnO in the PCMS-1. Raman is a powerful tool for analyzing the structure of oxides. From the Figure S5, two obvious peaks can be observed at 557 cm−1 and 1126 cm−1. The peak at 557 cm−1 can be assigned to the E1 (LO) vibration model of hexagonal wurtzite structure ZnO crystal. While the peak at 1126 cm−1 is due to multiple phonon scattering processes of Zn-O. The peaks located at 420 cm−1 is from the E2 (high) vibration model of Zn-O35. The normalized XAES of PCMS-1 and corresponding EXAFS (extended x-ray absorption fine structure) are provided to give the further insight. The corresponding Fit parameters are shown in Table 1. We can see that the N value of Zn-S (N = 3.5) in PCMS-1 is close to that of standard ZnS (S-ZnS) (N = 4), indicating the existence of ZnS as the major phase of PCMS-1. The slight low N value of Zn-S (3.5 vs 4) also implies the presence of slight ZnO in PCMS-1. In addition, the lower N value of Zn-S-Zn (4.5) for PCMS-1 than that for S-ZnS (12) implies the small size of ZnS grain in PCMS-1. Notably, the Zn-O can be observed in PCMS-1 with N value of 1, more lower than 3.9 in bulk ZnO36. Generally, the low N value implies the small size of the particles. Typically, for single atom Ag chain, the N is 2, more lower than 12 for bulk Ag37. A single atom Pt has no shown any Pt–Pt contribution38. Therefore, the low N value of Zn-O implies the partial replacement of surface S atom in ZnS by O, and the formation of the ZnO-dotted ZnS clusters.

Bottom Line: Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE.As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition.The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin 150080 (P. R. China).

ABSTRACT
The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy "controlling competitive reaction" strategy by selecting the thiourea as S(2-) source and Zn(Ac)₂·2H₂O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m(2)g(-1), microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

No MeSH data available.